Tailgates and particularly tailgates which are used as lifting platforms for lifting a load to the level of the floor of a truck are of a heavy construction and require the exercise of considerable force in order to pivot the tailgate from its horizontal opened position to its upright closed position.
Torsion bars are commonly provided for the purposes of assisting the manual opening and closing of the tailgate. In order to ensure that the tailgate will remain in an opened position in use the torsion bars do not have sufficient power to automatically pivot the tailgate from the horizontal positon to the upright position.
Other power operated mechanisms have been proposed for use in providing a positive drive for driving the tailgate between its horizontal position and its vertical position for opening and closing the tailgate. These mechanisms have, however, been complex mechanisms which include a power transmission mechanism which extends from the frame to the platform and which are easily damaged in use because of the fact that they are exposed to the harsh environment in which these vehicles are required to operate.